Used motor oil has been estimated as being generated in the United States at a rate of about 1.1 billion gallons per year. Some of this used oil has been used as furnace oil and some has been used on rural dirt roads for dust control. Much of the oil has been merely discarded in sewers, dumps, and back alleys. With the ever decreasing petroleum reserves, it becomes more and more essential that this used oil be saved and used as long as possible.
One major obstacle to re-use of used oil in many applications involves the presence of various ash-forming impurities that remain dispersed in the oil due to the very effective dispersant characteristics of the additives in modern day lubricant systems.
Materials contained in a typical used crankcase oil that are considered to contribute to the ash content of the oil include sub-micron size carbon particles, inorganic materials such as atmospheric dust, metal particles, lead and other metal compounds originating from fuel combustion. Besides lead, which is generally present at concentrations of 1.0 to 2.5 weight percent, appreciable amounts of zinc, barium, calcium, phosphorus and iron are also present in the used crankcase oil. Examination of the used oil under an optical microscope at 600 magnifications reveals the very effective dispersant characteristics of modern day lube oils. The particle size of the particulates is estimated from this microscopic examination to be 0.1-1.0 microns with virtually no occurrence of agglomerates in the oil.
The presence of the ash-forming components in used oil puts limits on the extent to which the material can be used economically without ecological damage. For example, reuse of the used oil as fuel oil can give rise to serious atmospheric pollution when the oil contains in excess of one percent lead. Also, such fuel oil often results in burner and refractory maintenance costs that offset the purchase price differential between used oil and regular furnace oil.
Clearly, it is in the national interest to provide economical ways of removing the impurities from used oil so that it can be reused practically.
Recently, a technique of purifying used oil has been developed in which the used oil is reacted with an aqueous solution of an ammonium salt treating agent, then the water phase is removed, and the resulting oil phase-containing mass is separated by filtration. Such a technique is described in U.S. Pat. No. 4,151,072, the disclosure of which is incorporated herein by reference.
It is an object of this invention to provide an improvement on the method disclosed in U.S. Pat. No. 4,151,072.
In another aspect it is an object of the present invention to provide a means of obtaining from used motor oil a plurality of oil fractions suitable for reuse in forming blended oil formulations.
One embodiment of this invention provides a means of obtaining such useable fractions without the use of hydrotreating.
Another embodiment of this invention provides a means of reducing the severity of the conditions to which a hydrotreating catalyst must be exposed to produce the desired fractions.
Still another object of the present invention is to increase the catalyst life of the employed hydrotreating catalyst.
Still yet another object of the present invention is to reduce the amount of hydrogen needed in the reclaiming process.